I needed to work out some technical issues for the shell commission so I decided to experiment with them on the second piece of my Flag Series. The major issue I'm dealing with is how to bleach the wood so that I can get true colors. I haven't found any detailed info on the web but found enough to learn that I wanted to use a two part method with lye and hydrogen peroxide. Finding lye was more difficult than I envisioned. It seems that in recent years many hardware stores have stopped selling it, I assume because it is deceptively innocuous. It doesn't look any more dangerous than mayonnaise but will dissolve/burn your skin like sulfuric acid. Home Depot used to sell a brand that was made for paint stripping but I couldn't find it anywhere. After an extending Internet search I learned that it is still used for clearing clogged pipes and after a few local phone calls, I was able to find it at Agway. The 2 lb container was about $10. Hydrogen peroxide was a lot easier to find at the local drug store, costing $1 (3% solution) and, of course, vinegar is needed to neutralize the lye, easily picked up at the grocery store for about $2/gallon. I've read that there are commercial bleaching kits that use this chemicals and can be bought at hardware stores but I haven't seen them -- admittedly, I haven't I looked very hard either. Having a kit has the huge advantage of providing instructions, I suspect they might also have higher concentrations of hydrogen peroxide which might work better, but they have the disadvantage of not being as much fun to use. I find learning by experimentation is more fun than reading.
Above are the three chemicals on top of some of the yellow birch I'm planning on using for the shell.
Here is the bird's-eye maple, with a large section of dark heart wood, that I'm using for the flag - before treatment.
This is what it looks like after applying the lye and hydrogen peroxide. I mixed about one teaspoon of lye with a half cup of water. Let it dissolve and cool down (the reaction of water and lye creates a lot of heat, if the concentration is too high, I suspect it would melt a plastic cup). Then I brushed the lye on the wood and let it sit for about 15 minutes (I've learned not to leave the brush in the lye mixture because it will dissolve the bristles). Then I brushed on the hydrogen peroxide, let it sit for a minute or two, wipe-off with paper towels, and repeated until I no more color was being removed (about five interations).
The next step is to brush on vinegar, wipe-off, and repeat two or three times. Remember, vinegar is cheap, don't be frugal with it. If the lye hasn't been completely neutralized, it will destroy your finish. The reaction of the vinegar with the wood is when you really see the change. Before the vinegar is applied, you might not think that you've done anything. After wiping off the last interation of vinegar I wash the piece with tap water to get rid of the vinegar smell.
Here is the "after" next to the board it came from.
And here is the early draft of an almost square flag (it is 1/8" wider than high because I couldn't bring myself to take another 1/8" off the bird's-eye maple).
Update August 30, 2011: For people looking for more information, check out this discussion on the WoodWeb site.